Air supply for a blast furnace



Nov. 9, 1965 E. B. DUNKAK AIR SUPPLY FOR A BLAST FURNAGE Filed Aug. l5, 1962 MM5/V70@ .5M/Me gjm/KHK M Q W rfaewfy United States Patent 3,216,712 AIR SUPPLY FOR A BLAST FURNACE Elmer B. Dunkak, Palm Beach, Fla., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Aug. 15, 1962, Ser. No. 217,090 Claims. (Cl. 26o-13) This invention relates to a device for supplying air to a blast furnace or the like requiring large volumes of hot air under pressure.

One feature of the invention is the use of a turbofan engine as a source of hot gas to power a free turbine which in turn drives a compressor for raising the fan air to the necessary pressure required for the furnace.

Another feature is a proportioning of the fan air between the compressor and the free turbine. Another feature is the use of a part of the free turbine power to drive a gas compressor by which to pressurize fuel gas for use in the turbofan engine.

Other features and advantages will be apparent from the specification and claims, and from the accompanying drawing which illustrates an embodiment of the invention.

FIG. 1 is a diagrammatic view showing an installation embodying the invention.

FIG. 2 is a longitudinal sectional View through the fan engine and associated devices.

As best shown in FIG. 1 a turbofan engine 2 is used in conjunction with a blast furnace 4 for supplying air at the necessary pressure and in the necessary quantity for charging the blast furnace. The blast furnace gases are discharged through a stack connection 6 to the stack 8, shown diagrammatically, and the stack is also connected through a duct connection 10 to the exhaust from the engine assembly.

As shown in FIG. 2, the engine includes a multistage fan 12 from which a part of the pressurized air is discharged into an annulus 14 surrounding a multistage compressor 16. This compressor receives the remainder of the pressurized air from the fan 12. The air from the compressor 16 passes through a combustion chamber 18 having a plurality of ametubes 20 and discharges through a turbine 22 which drives the compressor and fan. Fuel for the combustion chambers is delivered from a conduit 24 to a fuel manifold 26 from which it is discharged through nozzles into the flametubes.

A conduit 28 conveys fan air from the annulus 14 to a chamber 30 provided by the powerplant and also into a space 32 between the compressor-driving turbine 22 and a free or power turbine 34. The duct 28 may have a valve 35 therein downstream of the outlet to the space 32 so that by adjustment of this valve the quantity of air delivered to the chamber 30 may be proportioned exactly to the blast furnace requirements. With this arrangement, a part of the fan air is mixed with the exhaust gas from the turbine 22 for driving the free turbine 34. The combined gases exhausting from the turbine 34 flow through an exhaust duct 36 into the stack connection 10.

The free turbine 34 is connected by a shaft 38 to a centrifugal pump 40 which takes air from the chamber 30, that is to say, the fan-pressurized air and raises the pressure to a suitable pressure for delivery into the blast furnace. From the outlet 42 of the fan a duct 44 delivers this pressurized air to the air inlets 46 for the blast furnace. These air inlets are connected to a manifold 43 which in turn is connected to the duct 44, as shown.

The power turbine 34 may also drive a second centrifugal pump 50 mounted on an extension 38 of the shaft 38. This pump takes fuel gas from a chamber 52 and delivers it to a pump outlet 54 connected by a duct 56 to the fuel supply duct 24 for the engine. The pump increases the fuel gas pressure so that it is higher than the air pressure in the combustion chamber. It is well known that there is frequently a supply of fuel gas available in areas where blast furnaces are in use and this permits use of such gas as fuel for the turbofan.

It has been found that the pressures available in a power assembly of this type are particularly adapted for the supply of air under pressure to a blast furnace. The use of such an engine replaces the extensive assemblage of reciprocating compressors, heat exchangers and gas heaters which are so well known to be necessary in the usual air supply systems for blast furnaces.

In an installation of this character, the turbofan receives air at atmospheric pressure and normal outdoor temperature and raises the pressure and temperature of the air. For example, one particular fan engine has an inlet flow of 385 lbs., of air per second. The portion of this air discharging from the fan 12 into the annulus 14 is about 220 lbs. per second which has a pressure of about 25 p.s.i.a. and the temperature is increased about 100. The remainder of the air which ows through the compressor 16 and through the turbine 22 discharges from the turbine 22 at about 850 F. and at a pressure of about 24 p.s.i.a. About 60 lbs. of air from the duct 28 discharges into the chamber 32 and mixes with the hot gas discharged from the turbine 22 such that about 225 lbs. of air per second is used in driving the turbine 34. The remainder of the air in the duct 28 is delivered to the compressor 40 from which it is discharged at about 50 p.s.i.a. and at a temperature of about 325 F. This is about lbs. of air per second and is substantially the amount of air needed for the furnace. This air is pressurized by the fan 12 and compressor 40 to the desired pressure for supply to the blast furnace. Obviously, adjustment of valve 35 permits adjustment of the quantity of air entering chamber 30.

It has been found that this system is lighter in weight, less complex, smaller in size and substantially lower in cost than the conventional steam or electrically driven blower systems regularly used in blast furnace operation.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. A device for supplying hot gas under pressure to a blast furnace, including a turbofan engine, a free turbine driven by the exhaust gas from the engine, an air compressor driven by the free turbine, ducting by which fan air from the engine is delivered to the air compressor to be compressed, means for delivering a part of the fan air to the exhaust gas from the turbofan engine, and means for delivering the compressed air from the compressor to the blast furnace.

2. A device as in claim 1 in which there is a second compressor also driven by the free turbine, means for supplying fuel gas to the inlet to the second compressor and means for delivering the fuel gas from the discharge of the second compressor to the engine as fuel.

3. A device as in claim 1 in which there is a valve by which to control the portion of the fan air delivered to the air compressor to adjust to the quantity of air required for normal blast furnace operation.

4. A device for supplying hot gas under pressure to a blast furnace or the like, including a turbofan engine, a free turbine driven by the exhaust from the engine, an air compressor driven by the free turbine, means for ducting a part of the air from the turbofan to said air compressor, and means for ducting the remainder of the air from the turbofan not entering the air compressor to mix With the exhaust gas from the engine upstream References Cited by the Examiner of the free turbine to increase the free turbine power,

and valve means in one of said ducting means for con- UNITED STATES PATENTS trolling the portion of turbofan air delivered to said air 2,632,297 3/53 ogston 60 39 17 COHIPYCSSOI'- 5 2,701,443 2/55 Sedille 60-39.17

5. A device as in claim 4 in which a gas compressor is also driven by the free turbine for compressing fuel JOHN F' CAMPBELL Primary Examiner.

gas to a pressure adequate for injection of the gas into the engine. JAMES H. TAYMAN, JR., Examiner. 

4. A DEVICE FOR SUPPLYING HOT GAS UNDER PRESSURE TO A BLAST FURNACE OR THE LIKE, INCLUDING A TURBOFAN ENGINE, A FREE TURBINE DRIVEN BY THE EXHAUST FROM THE ENGINE, AN AIR COMPRESSOR DRIVEN BY THE FREE TURBINE, MEANS FOR DUCTING A PART OF THE AIR FROM THE TURBOFAN TO SAID AIR COMPRESSOR, AND MEANS FOR DUCTING THE REMAINDER OF THE AIR FROM THE TURBOFAN NOT ENTERING THE AIR COMPRESSOR TO MIX WITH THE EXHAUST GAS FROM THE ENGINE UPSTREAM OF THE FREE TURBINE TO INCREASE THE FREE TURBINE POWER, AND VALVE MEANS IN ONE OF SAID DUCING MEANS FOR CONTROLLING THE PORTION OF TURBOFAN AIR DELIVERED TO SAID AIR COMPRESSOR. 